--- title: Recapping the London Mercurial sprint | daily.dev description: The Mercurial development team held a 3-day sprint in London hosted by Jane Street, gathering nearly 20 contributors. Key topics included: a FUSE-based Virtual... canonical: https://daily.dev/posts/recapping-the-london-mercurial-sprint-d8vx8xdmw twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Recapping the London Mercurial sprint | daily.dev og:description: The Mercurial development team held a 3-day sprint in London hosted by Jane Street, gathering nearly 20 contributors. Key topics included: a FUSE-based Virtual... og:url: https://daily.dev/posts/recapping-the-london-mercurial-sprint-d8vx8xdmw og:image: https://api.daily.dev/og/posts/d8VX8XDMw.png og:image:alt: Recapping the London Mercurial sprint og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Recapping the London Mercurial sprint **[Lobsters](https://daily.dev/sources/lobsters)** · 12 min read · 0 upvotes · 0 comments ## Summary The Mercurial development team held a 3-day sprint in London hosted by Jane Street, gathering nearly 20 contributors. Key topics included: a FUSE-based Virtual File System that reduced working copy initialization from 20s+ to under 2s; first-class conflict handling inspired by Pijul and Jujutsu; a new 'Hyperlog' storage format (revlog V2) with mutable index entries, unified filelogs, and better transactionality; 'store shapes' as a replacement for the brittle narrow extension; scaling improvements for obsmarker exchange and bundle caching; Changeset Evolution discussions with GitButler; and plans for Mercurial to act as a high-performance Git server. Multiple bug fixes, documentation updates, and Heptapod releases were also shipped during the sprint. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What performance improvement did Mercurial's experimental FUSE-based virtual file system achieve for large working copies? The experimental read-only FUSE-based VFS reduced time to first interaction for a new working copy from over 20 seconds down to under 2 seconds in worst-case scenarios, with only a 10-20% overhead during normal operations. It uses an overlay filesystem to support writes and is already being used by real users. _Developers working with large Mercurial repos track VFS and scaling developments like this on daily.dev._ ### What is the Mercurial Hyperlog and how does it differ from the existing revlog format? Hyperlog is the nickname for revlog V2, Mercurial's next-generation storage format under development. It adds mutable index entries, multiple index and data blocks for extensibility and memory locality, sparse files with default values, better transactionality, and unified filelogs that massively reduce the number of files on disk. The current revlog V1 has been in use for over 20 years. _Engineers evaluating VCS storage architecture can follow Mercurial internals discussions on daily.dev._ ### What are Mercurial store shapes and how do they improve on the narrow extension? Store shapes are a server-side configuration model introduced in the 7.2 cycle to replace the brittle narrow extension for partial history clones. Advantages include composable includes/excludes, fingerprinting for equivalent patterns, enforced server-client agreement on patterns, client notification of server-side changes, a foundation for permissions systems, and support for clonebundles for common patterns. _Teams using partial clone workflows in large repos can track Mercurial narrowing improvements on daily.dev._ ## Similar posts on daily.dev - [Mercurial, 20 years and counting: how are we still alive and kicking?](https://daily.dev/posts/mercurial-20-years-and-counting-how-are-we-still-alive-and-kicking--kfgl4thg1) · Hacker News · 0 upvotes · 0 comments - [How Our Community Shipped 66 Git Improvements In Under 2 Months — Zed's Blog](https://daily.dev/posts/how-our-community-shipped-66-git-improvements-in-under-2-months-zed-s-blog-o4wtqp3co) · Zed · 35 upvotes · 2 comments - [A summary from the 2026 Git Contributors' Summit](https://daily.dev/posts/a-summary-from-the-2026-git-contributors-summit-tcswiawyx) · LWN.net · 0 upvotes · 0 comments - [JJ Con 2026 Talks are Up](https://daily.dev/posts/jj-con-2026-talks-are-up-yygn33yxk) · GitButler Blog · 6 upvotes · 0 comments - [SymfonyLive Berlin 2026: “Git, But Better: An Introduction to Jujutsu \(jj\)” \(Symfony Blog\)](https://daily.dev/posts/symfonylive-berlin-2026-git-but-better-an-introduction-to-jujutsu-jj-symfony-blog--wxvwltz52) · Symfony · 1 upvotes · 0 comments --- Tags: [#version-control](https://daily.dev/tags/version-control) [View this post on daily.dev](https://daily.dev/posts/recapping-the-london-mercurial-sprint-d8vx8xdmw) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"Recapping the London Mercurial sprint","url":"https://daily.dev/posts/recapping-the-london-mercurial-sprint-d8vx8xdmw","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/recapping-the-london-mercurial-sprint-d8vx8xdmw"},"datePublished":"2026-08-07T22:26:14.393Z","dateModified":"2026-08-07T22:26:45.820Z","description":"The Mercurial development team held a 3-day sprint in London hosted by Jane Street, gathering nearly 20 contributors. 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